Improving the hemocompatibility of a porohyperelastic layered vascular graft using luminal reversal microflows

A custom CellScale tubular mechanical testing system, described in this publication as a ‘custom-made microbiaxial tensile testing device,’ was used to mechanically characterize single-layer tubular electrospun Tecoflex SG-85 A and thermobonded polycaprolactone constructs. This is the earlier publication from the same University of Pittsburgh research group using the custom CellScale tubular testing platform. Three specimens of each material were cut into 1-1.5 cm tubular segments, cannulated onto metallic capillary tubes, sutured, and glued at both ends. The CellScale testing chamber was filled with water and maintained at 37 °C. The graft inlet was connected to a water-filled hydraulic piston and pressure line, while the outlet was blocked to create closed-end pressurization. A pressure transducer monitored intraluminal pressure, a load cell measured axial load, and the system camera tracked outer diameter. Specimens underwent 10 loading-unloading cycles between 0 and 120 mmHg, with the first nine serving as preconditioning and the final cycle used to calculate circumferential Cauchy stress-stretch behavior. The axial position was fixed during testing and no axial displacement was imposed. CellScale measurements showed that electrospun Tecoflex was substantially more compliant than thermobonded PCL: maximum circumferential stretch was approximately 1.12 for Tecoflex and 1.008 for thermobonded PCL, and Tecoflex had a significantly lower tangential modulus. These experimentally measured responses were used to identify Neo-Hookean material parameters for the study’s porohyperelastic finite element model, which subsequently predicted luminal reversal flow and compliance in the bilayered high- and low-LRF vascular graft designs.